1. Field
The invention is in the field of machines for separating meat from bone and from so-called "bony" matter which includes connective and other heavy tissues, skin, etc. Such machines have become known as "deboning" machines and comprise a conveying screw rotating within a tubular conduit that is provided with a multiplicity of small holes as a screen through which the relatively soft meat component is extruded under pressure as the bone and bony matter is advanced to a discharge outlet that is usually provided with a restrictive ring valve arrangement for effecting and controlling back-pressure within the machine.
2. State of the Art
Deboning machines have evolved through the years from that disclosed by McFarland U.S. Pat. No. 3,739,994 issued Jun. 19, 1973 (reissued Jul. 17, 1984 under Re. U.S. Pat. No. 31,631), which was the first to provide for the building up of a filter mat along the inside surface of a perforate tubular conduit as a screen through which the meat must pass before being expelled as filtered largely free of bone particles. The desired filter mat was created by leaving a small clearance between the outer edge surface of the spiral flights of an auger feed screw and the inner surface of the screen. The bone and bony matter was passed through an adjustably restrictive, annular orifice formed between the inside surface of a ring movable longitudinally relative to an extension of the auger screw and leading to a discharge outlet for the bone and bony matter. An additional feature was the provision, in an alternative embodiment of the machine, of a pair of knife blades freely inset into receiving notches in and along the flights of the auger screw, with sharp edges of such blades bearing lightly against the inner wall of the screen so as to cut fibers that create drag, but without destroying the filter mat.
U.S. Pat. No. 4,189,104 of Feb. 19, 1980 to Claudio dos Santos discloses an improved machine, wherein the face of the ring valve confronting the advancing bone and bony material being passed to and through the restrictive annular orifice is scalloped to cooperate with a correspondingly scalloped end portion of the auger screw extension in effecting a more rapid passage of material through the machine to increase output per unit time.
McFarland U.S. Pat. No. 4,566,640 of Jan. 28, 1986 speaks of grooves and vanes (the lands between the grooves) on an extension of the auger screw for grinding or chopping disjointed neck or spinal bones into sufficiently small particles to pass through the restricted annular orifice between the stationary ring and the extension portion of the rotating auger screw.
Machines of a type that have been made to operate on relatively large, unground pieces of meat and bone have suffered by low throughput and failure to cope with the larger pieces of bones, heavy tissues, and skin.